Means for securing turbine-rotors to their shafts



B. LJUNGSTRUM. MEANS FOR SECIURING TURBINE ROTORS TO THEIR SHAFTS=APPLICATION FILED MAR. 25, ,I9I9.

1,347, 343. Pat nt d uly 20, 1920.

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Inventor:

Bil" erLJun strim, by

His oqtto neg.

UNITED STATES PATENT OFFICE;

BIB-GER LJUNGSTRbM, F STOCKHOLM, SWEDEN, ASSIGNOR TO AKTIEBOLAGETLJ'UNGSTRbMS ANGTURBIN, A. CORPORATION OF SWEDEN.

MEANS FOR SECURING TURBINE-ROTORS TO THEIR SHAFTS.

Patented July 20, 1920.

' Application filed March 25, 1919. Serial No. 285,032.

To all whom it may concern:

Be it known that I, BrRoER LJUNos'rRoM, 21 Narnavagen, Stockholm, in theKingdom of Sweden, have invented certain new and useful Improvements inMeans for Securing Turbine-Rotors to Their Shafts, of which thefollowing is a specificatlon.

The present invention relates to means for securing turbine rotors totheir shafts and has for its object to provide means for keeping theparts tight at all times.

For a consideration of what I believe to be novel and my invention,attention is directed to the accompanying description and claimsappended thereto.

In the accompanying drawing which illustrates one of the embodiments ofmy invention, Figure 1 is an axial section of a turbine shaft and a partof the rotating blade element or rotor carried thereby, taken on line1-1 of Fig. 2; Fig. 2 is an end view of the shaft and portion of therotor, and Fig. 3 is a detailseotional view taken on line 3-3 of Fig. 2.v I

1 indicates a part of a rotor upon which are mounted concentric rows ofblades 2. In the type of turbine to which my invention more especiallyrelates two rotors are provided arranged face to 'face with concentricrows of axially extending blades between and through which the steamflows radially outward. The rotor is provided with a hubv 3 containingslots 4 through which steam flows from a suitable source to the innerblade ring. The hub is provided with a conical bore to receive one endof the stub shaft 5, and the two parts are held against relativerotation by a plurality of equally spaced keys 6 which mayadvantageously be made of round stock finished to the required size,These keys have a slight taper from their inner to their outer ends sothat when moved outwardly from the center ofthemachine they will preventan v on its outer'end which is secured to the main shaft 8 by aseries ofequally spaced bolts 9, a shoulder 10 .betweenthetwo serving to holdthem central. The main shaft is mounted in a suitable bearing 8 havingthe usual babbit or other lining containing suitable oil grooves.

In any turbine, and particularly one where boiler steam is-admitteddirectly to.

the rotor in the manner illustrated, the hub service.

ion shoulder on the shaft.

of the rotor expands due to increase of temperature and if it does sofaster than the shaft it will become loose thereon. A loose rotor ishighly objectionable since it causes more or less violent vibrations,depending upon the degree of looseness. These vibratlons sometimes causeconsiderable damage to the blades, packings, etc.', and if seriousrequire the machine to I avoid this objection by the following means Thestub shaft is made hollow and inside of it is a long, tubular tensionmember 11 having a shouldered head on the outer end which-is snuglyfitted to a compan- The purpose in making the member hollow is to permitsteam to enter it so that it and the stub shaft will be heated tosubstantially the same temperature as the hub of the rotor. The

stub shaft and tension member are prevented from'turning independentlyof each other by a suitable means, a screw being shown for the purpose.Near the inner, end the tubular member is provided with a guidingsurface 12 which makes a good sliding fit with the inner wall or bore-ofthe stub shaft so as to hold the parts in their proper relation. Theinner end ofthe member is provided with a coarse screw thread to receivethe nut 13, the latter serving as a means for putting the member 11under tension. To prevent the faces of the nut and hub from directlyengaging a washer 14 of different metal either harder or softer isinterposed between the two.

By calculation or experiment or both I determine how much the bore ofthe hub will enlarge due to temperature changes. It is evident thatifthe hub expands more quickly than the shaft it will become loose. Itis further evident since the contacting surfaces of the shaft and wallof the bore areconical that the parts can again be made tight if somemeans is provided which acts when'the hub is in its expanded conditionto draw the stub shaft and hub together.

Such a means is found in the tension member 11 and nut 13. Havingdetermined what the maximum enlargement of the hub will be and how muchaxial movement is necessar to bring the parts into firm contactv underal conditions, I so design said tension member that it will, when cold,be stretched by an amount somewhat greater than the total amount ofrelative axial movement between the hub and stub shaft I at any time. Asa result of this when the hub enlarges for any reason the tension memberwill force the hub farther on to the shaft with the result of keeping ittight. The hub may be advanced on the shaft by one or by severalsuccessive heatings of the sired but I prefer to make it hollow becauseit is highly desirable to heat it and also the hub and shaft to asnearlythe same temperature as possible. The outer end of the member isscrew-threaded to receive the nut 15 which prevents steam from passingthrough it into the 'oint between the stub and main shafts.

preferably threaded at 16 so that when it is desired to remove the rotorfrom the stub shaft a bar may be threaded intothe opening until itengages the nut 15 and by turning the same the member will be put underadditional tension with the result of taking pressure off of the nut 13and permitting it to be easily removed.

To make sure that the nut 13 does not work loose while the machine is inoperation, it is provided with a number of equally spaced holes 17arranged in a circle. In the adjacent part or parts are similar holes 18arranged in a circle of the same diameter, the number however, differingfrom that in the nut. After the nut is screwed to its seat, a copper orother pin 19 is driven into the registering holes and slightly upset onits inner end. This looks the arts against relative angular movement. 0take off the nut the pin is first drilled out after which the nut can berotated as usual. I may, however, in some cases use an ordinary setscrew with apointed end.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof;

but I desire to have it understood that the apparatus shown is onlyillustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. In a turbine, the combination of. a

rotor, a hollow shaft having a tapered end to which the rotor is keyed,a tension member which is carried by the shaft, and means he inner endis also a plurality of ho mounted on the member for holding the rotor onthe shaft. and said member under tension.

2. In a turbine, the. combination of a rotor, a hollow shaft having ataper at one end upon which .the rotor is, keyed and a shoulder at apoint remote from said end, a tension member which is seated on theshoulder and extends inwardly beyond the hub of the rotor and has ascrew-threaded end, and a nut which holds the rotor on the shaft againstaxial 'movement and also keeps said member under tension.

3. In a turbine, the combination of a bladed rotor having .a hub withopenings therein through which steam flows to the blades, a hollow shafthaving a taper at its inner end to receive the rotor, a hollow tubularmember located in the shaft and to which steam from said openings isadmitted, and a shoulder and nut on the ends of the member one of whichengages the shaft and the other the rotor, said nut and shoulder hold-Jing the hub against axial movement and also maintaining said member intension.

4. In a turbine, the combination of a I rotor, a hollow stub shaft whichhas a taper on its inner end on which the rotor is mounted and a flangeand shoulder at its outer end, a tubular member which is seated on theshoulder at its outer end, a mm on the inner-end of the member whichmaintains it in tension and holds the rotor on the'shaft,

and a main shaft' which is secured to the stub ihzltft by a centeringshoulder and retaining 5.- In a turbine, the combination of.a rotorhaving a tapered bore, a shaft having a tapered endupon whichthe rotoris mounted, tapered keys which prevent the rotor from turning on'theshaft, a member located within-the shaft, and anut and shoulder on themember, one ofwhich engages the shaft, and the other the rotor, saidshoulder and nut serving to hold the member in tension at all times andmove the rotor and keys axially on the shaft when the rotor enlargesfaster than the shaft.

I 6. In a turbine, the combination of -a 4 rotor, a shaft having a taperupon which the rotor is mounted, a tension member within the shaft whichis anchored at one end and is provided with a screw thread at the other,

a nut on the member which maintains it in tension and holds the rotor onthe shaft, said nut and rotating parts being provided with es arrangedin circles of the same diameter, the num r of holes in the nut differingfrom that in aid parts, and

' a metal plug which is inserted in a pair of registering holes toprevent relative angular movements of the nut and said arts.

In witness whereof, 'I have ereunto set my hand this 4th day ofFebruary," 1919.

BIRGER LJUNGSTRCM.

